We've seen our share of Sitelinks tests in Google Search. Including a number of variations around sitelinks. But here is a version where you can click an arrow down to expand and show more sitelinks.
Punit spotted this example, where Google is showing this arrow down button that will show you a second line of sitelinks when you expand it.
Here is a screenshot he shared on Bluesky:
Here is a video of it in action:
Forum discussion at Bluesky.
